This work presents the physical-thermal and mechanical characterization of a low-density polyethylene (LDPE)-Al matrix composite material that was obtained from reinforcing recycled (post-consumer) long-life Tetra Pak packages with fique natural fibers from southwestern Colombia. The fique was subjected to three chemical treatments to modify its surface (alkalinization, silanization and pre-impregnation with polyethylene) to increase the quality of its interfaces. Additionally, panels with 10%, 20%, and 30% v/v of fiber were manufactured by the hot compression molding. The mechanical properties of the different composite materials showed that the pre-impregnation treatment promoted a significant increase in the tensile and flexural properties with respect to the fiber-reinforced composite without surface modification. Additionally, in materials with 30% fibers that were treated with pre-impregnation, there was a decrease in the water absorption capacity of 53.15% when compared to composites made with 30% native fibers. Finally, increases in the fiber content mainly caused better mechanical performances, which increased as a direct function of the amount of fique incorporated.

Abstract. Multiwall carbon nanotubes (MWCNTs) previously treated with a cationic polymer were incorporated on the surface of carbon fibers modified by three different chemical treatments, namely, oxidation, oxidation-silanization and oxidation-pre-impregnation. Prior to the incorporation of the MWCNTs, the physical surface properties of the fibers were studied by contact angle and the chemical surface properties by X-ray photoelectron spectroscopy (XPS). The interfacial shear strength (IFSS) of the different systems carbon fiber-MWCNTs-matrix was evaluated using the single-fiber fragmentation test (SFFT) and it was observed that the IFSS of the oxidized-pre-impregnated fibers, was considerably higher than that observed for the other fiber-matrix systems. This was attributed to enhanced interfacial interactions because the fiber surface treatments improved the wettability of the carbon fiber and the MWCNTs, which resulted in a better fiber-matrix mechanical interlocking and to the formation of covalent bonds between the different phases of the composite.

Biocomposites were prepared from a ternary matrix of polylactic acid (PLA), polycaprolactone (PCL), and thermoplastic starch (TPS) and reinforced with native fique fibers from southwestern Colombia. The influence of surface modification by alkalization of fique fibers on the interfacial properties of the biocomposite was studied using pull-out tests. Additionally, the effect of short fique fibers in three proportions (10%, 20%, and 30% (w/w)) on the tensile mechanical properties of the composite was evaluated. The experimental results indicated that the interfacial shear strength (IFSS) of the ternary matrix was predominantly influenced by PCL and characterized by the development of a weak interface that failed due to matrix yielding. Furthermore, the incorporation of short fique fibers increased the elastic modulus of the composite to values similar to those estimated with the Tsai–Pagano model. The alkalization treatment of the fique fibers improved the interface with the composite matrix, and this phenomenon was evidenced by the results of the micromechanical and tensile characterizations of the composite.

Background: Provisional abutments are widely used in the rehabilitation of dental implants as it allows the use of a provisional crown in order to restore patient aesthetics while the final restoration is being carried out; most of the temporary abutments available on the market are made of titanium alloygrade V (type Ti-6Al-4Va) and polyetheretherketone (PEEK), a material that exhibits very low adhesion to polymethylmethacrylate (PMMA). Objective: This research is aimed to compare the mechanical properties of commercially available PEEK abutments and abutments made using an additive technique with photopolymeric resin. Methods: Eighteen commercial temporary abutments manufactured in PEEK and eighteen experimental abutments manufactured by 3D printing using photopolymeric resin were used. The two groups of abutments were subjected to compression, bending and adhesion tests using six abutments of each type by test. Statistical analysis was performed with STATA 14 software. The data were analyzed by means of the Wilcoxon Mann-Whitney test, as these were two independent samples of reduced size. Values ​​lower than (p <0.05) were considered statistically significant in all tests and rejected the null hypothesis of equality between the group medians. Conclusion: The results indicate that it is possible to make abutments with good mechanical properties in photopolymeric resin (CLEAR FLGP04) using additive techniques to be used as temporary abutments.

This paper presents a comprehensive study on the impact of surface modification of carbon fibers using multiple-walled carbon nanotubes (MWCNTs) to improve the load-transfer capacity of the fiber-matrix interface of an epoxy matrix composite subjected to dynamic loads. The single-fiber fragmentation technique (SFFT) was utilized to characterize the length of interfase damage (IDL) produced by quasi-static and dynamic loadings for linear elastic and plastic strains and the residual efficiency of interfacial stress transfer. A finite element model was used to validate the optical measurement and the extent of interfase damage. Scanning electron microscopy (SEM) corroborated the presence of the MWCNTs on the surface of the carbon fibers. The interfacial shear strength (IFSS) increased by approximately 27.5%, attributed to the carbon nanotubes and a more significant fiber-matrix stress transfer. The application of dynamic loads decreased the mechanical properties of the matrix, premature fragmentation of the carbon fiber, and interfacial damage, which led to a reduction in the interfase load-transfer capacity. However, the incorporation of carbon nanotubes in the interface decreased the adverse effects generated by the application of cyclic loads, mainly the propagation of interfacial damage.